Spine implant with a dual deflection rod system including a deflection limiting sheild associated with a bone screw and method

ABSTRACT

A dynamic stabilization, motion preservation spinal implant system includes a deflection rod system implant. The system is modular so that various constructs and configurations can be created and customized to a patient.

CLAIM TO PRIORITY

This application claims priority to all of the following applicationsincluding U.S. Provisional Application No. 60/942,162, filed Jun. 5,2007, entitled “Dynamic Stabilization and Motion Preservation SpinalImplantation System and Method” (Attorney Docket No. SPART-01010US0),

U.S. patent application Ser. No. 11/832,260, filed Aug. 1, 2007,entitled “Shaped Horizontal Rod for Dynamic Stabilization and MotionPreservation Spinal Implantation System and Method” (Attorney Docket No.SPART-01006US0),

U.S. patent application Ser. No. 11/832,273, filed Aug. 1, 2007,entitled “Multi-directional Deflection Profile for a DynamicStabilization and Motion Preservation Spinal Implantation System andMethod” (Attorney Docket No. SPART-01007US0),

U.S. patent application Ser. No. 11/832,305, filed Aug. 1, 2007,entitled “A Horizontal Rod with a Mounting Platform for a DynamicStabilization and Motion Preservation Spinal Implant System and Method”(Attorney Docket No. SPART-01008US0),

U.S. patent application Ser. No. 11/832,330, filed Aug. 1, 2007,entitled “Multi-dimensional Horizontal Rod for a Dynamic Stabilizationand Motion Preservation Spinal Implantation System and Method” (AttorneyDocket No. SPART-01009US0),

U.S. patent application Ser. No. 11/832,338, filed Aug. 1, 2007,entitled “A Bone Anchor With a Yoke-Shaped anchor head for a DynamicStabilization and Motion Preservation Spinal Implantation System andMethod” (Attorney Docket No. SPART-01010US1),

U.S. patent application Ser. No. 11/832,358, filed Aug. 1, 2007,entitled “A Bone Anchor With a Curved Mounting Element for a DynamicStabilization and Motion Preservation Spinal Implantation System andMethod” (Attorney Docket No. SPART-01011US0),

U.S. patent application Ser. No. 11/832,377, filed Aug. 1, 2007,entitled “Reinforced Bone Anchor for a Dynamic Stabilization and MotionPreservation Spinal Implantation System and Method” (Attorney Docket No.SPART-01012US0),

U.S. patent application Ser. No. 11/832,400, filed Aug. 1, 2007,entitled “A Bone Anchor With a Compressor Element for Receiving a Rodfor a Dynamic Stabilization and Motion Preservation Spinal ImplantationSystem and Method” (Attorney Docket No. SPART-01013US0),

U.S. patent application Ser. No. 11/832,413, filed Aug. 1, 2007,entitled “Dynamic Stabilization and Motion Preservation SpinalImplantation System and Method with a Deflection Rod” (Attorney DocketNo. SPART-01014US0),

U.S. patent application Ser. No. 11/832,426, filed Aug. 1, 2007,entitled “Dynamic Stabilization and Motion Preservation SpinalImplantation System and Method with a Deflection Rod Mounted in CloseProximity to a Mounting Rod” (Attorney Docket No. SPART-01015US0),

U.S. patent application Ser. No. 11/832,436, filed Aug. 1, 2007,entitled “Dynamic Stabilization and Motion Preservation SpinalImplantation System and Method” (Attorney Docket No. SPART-01016US0),

U.S. patent application Ser. No. 11/832,446, filed Aug. 1, 2007,entitled “Super-Elastic Deflection Rod for a Dynamic Stabilization andMotion Preservation Spinal Implantation System and Method” (AttorneyDocket No. SPART-01017US0),

U.S. patent application Ser. No. 11/832,470, filed Aug. 1, 2007,entitled “Revision System and Method for a Dynamic Stabilization andMotion Preservation Spinal Implantation System and Method” (AttorneyDocket No. SPART-01020US0),

U.S. patent application Ser. No. 11/832,485, filed Aug. 1, 2007,entitled “Revision System for a Dynamic Stabilization and MotionPreservation Spinal Implantation System and Method” (Attorney Docket No.SPART-01021US0),

U.S. patent application Ser. No. 11/832,494, filed Aug. 1, 2007,entitled “Dynamic Stabilization and Motion Preservation SpinalImplantation System and Method” (Attorney Docket No. SPART-01022US0),

U.S. patent application Ser. No. 11/832,517, filed Aug. 1, 2007,entitled “Implantation Method for Dynamic Stabilization and MotionPreservation Spinal Implantation System and Method” (Attorney Docket No.SPART-01023US0),

U.S. patent application Ser. No. 11/832,527, filed Aug. 1, 2007,entitled “Modular Spine Treatment Kit for Dynamic Stabilization andMotion Preservation of the Spine” (Attorney Docket No. SPART-01024US0),

U.S. patent application Ser. No. 11/832,534, filed Aug. 1, 2007,entitled “Horizontally Loaded Dynamic Stabilization and MotionPreservation Spinal Implantation System and Method” (Attorney Docket No.SPART-01025US0),

U.S. patent application Ser. No. 11/832,548, filed Aug. 1, 2007,entitled “Dynamic Stabilization and Motion Preservation SpinalImplantation System with Horizontal Deflection Rod and ArticulatingVertical Rods” (Attorney Docket No. SPART-01029US0),

U.S. patent application Ser. No. 11/832,557, filed Aug. 1, 2007,entitled “An Anchor System for a Spine Implantation System That Can MoveAbout three Axes” (Attorney Docket No. SPART-01030US0,

U.S. patent application Ser. No. 11/832,562, filed Aug. 1, 2007,entitled “Rod Capture Mechanism for Dynamic Stabilization and MotionPreservation Spinal Implantation System and Method” (Attorney Docket No.SPART-01031US0),

U.S. Provisional Application No. 61/028,792, filed Feb. 14, 2008,entitled “A Deflection Rod System for a Dynamic Stabilization and MotionPreservation Spinal Implantation System and Method” (Attorney Docket No.SPART-01035US0),

U.S. Provisional Application 61/031,598, filed Feb. 26, 2008, entitled“A Deflection Rod System for a Dynamic Stabilization and MotionPreservation Spinal Implantation System and Method” (Attorney Docket No.SPART-01037US0), and

U.S. Provisional Application No. 61/057,340, filed May 30, 2008,entitled “A Spine Implant With A Deflection Rod System Aligned With ABone Anchor And Method” (Attorney Docket No.: SPART-01039US0).

All of the afore-mentioned applications are incorporated herein byreference in their entireties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to all of the following applicationsincluding U.S. patent application Ser. No. 12/______, filed May _(—),2008, entitled “A Deflection Rod System For A Spine Implant Including AnInner Rod And An Outer Shell And Method” (Attorney Docket No.:SPART-01035US1);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “A Deflection Rod System With A Deflection Contouring ShieldFor A Spine Implant And Method” (Attorney Docket No.: SPART-01035US2);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “Dynamic Stabilization And Motion Preservation SpinalImplantation System With A Shielded Deflection Rod System And Method”(Attorney Docket No.: SPART-01035US3);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “A Deflection Rod System For Spine Implant With End ConnectorsAnd Method” (Attorney Docket No.: SPART-01035US4);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “A Deflection Rod System For A Dynamic Stabilization And MotionPreservation Spinal Implantation System And Method” (Attorney DocketNo.: SPART-01035US5);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “A Deflection Rod System For A Dynamic Stabilization And MotionPreservation Spinal Implantation System And Method” (Attorney DocketNo.: SPART-01037US1);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “A Deflection Rod System With Mount For Dynamic StabilizationAnd Motion Preservation Spinal Implantation System And Method” (AttorneyDocket No.: SPART-01037US2);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “A Deflection Rod System With A Non-Linear Deflection To LoadCharacteristic For Dynamic Stabilization And Motion Preservation SpinalImplantation System And Method” (Attorney Docket No.: SPART-01037US3);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “A Deflection Rod System Dimensioned For Deflection To A LoadCharacteristic For Dynamic Stabilization And Motion Preservation SpinalImplantation System And Method” (Attorney Docket No.: SPART-01037US4);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “A Deflection Rod System For Use With A Vertebral FusionImplant For Dynamic Stabilization And Motion Preservation SpinalImplantation System And Method” (Attorney Docket No.: SPART-01037US5);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “A Dual Deflection Rod System For Dynamic Stabilization AndMotion Preservation Spinal Implantation System And Method” (AttorneyDocket No.: SPART-01037US6);

U.S. patent application Ser. No. 12/______, filed May _(—), 2008,entitled “Method For Implanting A Deflection Rod System And CustomizingThe Deflection Rod System For A Particular Patient Need For DynamicStabilization And Motion Preservation Spinal Implantation System”(Attorney Docket No.: SPART-01037US7);

U.S. patent application Ser. No. 12/______, filed ______, 2008, entitled“A Spine Implant With A Deflection Rod System Anchored To A Bone AnchorAnd Method” (Attorney Docket No.: SPART-01039US1);

U.S. patent application Ser. No. 12/______, filed ______, 2008, entitled“A Spine Implant With A Deflection Rod System Including A DeflectionLimiting Shield Associated With A Bone Screw And Method” (AttorneyDocket No.: SPART-01039US2);

U.S. patent application Ser. No. 12/______, filed ______, 2008, entitled“A Spine Implant With A Dual Deflection Rod System Including ADeflection Limiting Shield Associated With A Bone Screw And Method”(Attorney Docket No.: SPART-01039US4);

U.S. patent application Ser. No. 12/______, filed ______, 2008, entitled“A Spine Implant With A Deflection Rod System And Connecting LinkagesAnd Method” (Attorney Docket No.: SPART-01039US7); and

U.S. patent application Ser. No. 12/______, filed ______, 2008, entitled“A Spine Implant With A Deflection Rod System Aligned With A Bone AnchorAnd Method” (Attorney Docket No.: SPART-01039US8).

All of the afore-mentioned applications are incorporated herein byreference in their entireties.

BACKGROUND OF INVENTION

The most dynamic segment of orthopedic and neurosurgical medicalpractice over the past decade has been spinal devices designed to fusethe spine to treat a broad range of degenerative spinal disorders. Backpain is a significant clinical problem and the annual costs to treat it,both surgical and medical, is estimated to be over $2 billion. Motionpreserving devices to treat back and extremity pain have, however,created a treatment alternative to or in combination with fusion fordegenerative disk disease.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a posterior view of an embodiment of a dynamic spinestabilization system in accordance with the present invention.

FIG. 1B is a lateral view of the dynamic spine stabilization system ofFIG. 1A.

FIG. 2 is a posterior view of the dynamic spine stabilization system ofFIG. 1A implanted and extending between two vertebrae of a spine.

FIG. 3A is a posterior view of the dynamic spine stabilization system ofFIG. 1A implanted as shown in FIG. 2 and further comprising lockingscrews to resist rotation of the dynamic spine stabilization system.

FIG. 3B is a posterior view of another embodiment of the dynamic spinestabilization system of the invention.

FIG. 4 is a posterior view of another embodiment of the dynamic spinestabilization system of the invention.

FIG. 5 is a posterior view of another embodiment of the dynamic spinestabilization system of the invention.

FIG. 6 is a posterior view of yet another embodiment of the dynamicspine stabilization system of the invention including horizontal rods toresist rotation.

FIG. 7A is a posterior view of an alternative embodiment of a dynamicspine stabilization system in accordance with the present invention.

FIG. 7B is a lateral view of the dynamic spine stabilization system ofFIG. 7A.

FIG. 7C is a caudal view of the dynamic spine stabilization system ofFIG. 7A.

FIG. 8 is a posterior view of the dynamic spine stabilization system ofFIG. 7A implanted and extending between two vertebrae of a spine.

FIG. 9 is a posterior view of the dynamic spine stabilization system ofFIG. 7A implanted in an alternative arrangement to FIG. 8 and extendingbetween the two vertebrae.

FIG. 10 is a posterior view of yet another embodiment of a dynamic spinestabilization system in accordance with the present invention implantedand extending between two vertebrae of a spine.

FIG. 11A is a posterior view of an alternative embodiment of a dynamicspine stabilization system in accordance with the present invention.

FIG. 11B is a lateral view of the dynamic spine stabilization system ofFIG. 11A.

FIG. 12 is a lateral view of the dynamic spine stabilization system ofFIG. 11A comprising an alternative seating arrangement for a horizontalrod.

FIG. 13 is a posterior view of the dynamic spine stabilization system ofFIG. 11A implanted and extending between a vertebra of the spine and twoadjacent vertebrae.

FIG. 14A is a posterior view of an alternative embodiment of a dynamicspine stabilization system in accordance with the present invention.

FIG. 14B is a lateral view of the dynamic spine stabilization system ofFIG. 14A.

FIG. 15 is a posterior view of the dynamic spine stabilization system ofFIG. 14A implanted and extending between two vertebrae of a spine.

FIG. 16 is a posterior view of yet another embodiment of a dynamic spinestabilization system in accordance with the present invention implantedand extending between two vertebrae of a spine.

FIG. 17 is a lateral view of a further embodiment of a dynamic spinestabilization system in accordance with the present invention.

FIG. 18 is a lateral view of yet another embodiment of a dynamic spinestabilization system in accordance with the present invention.

FIG. 19 is a lateral view of a further embodiment of a dynamic spinestabilization system in accordance with the present invention.

FIG. 20A is an exploded perspective view of yet another embodiment of adynamic spine system in accordance with the present invention.

FIG. 20B is an perspective view the dynamic spin stabilization system ofFIG. 20A with the distraction rod system and set screw seated within theanchoring device.

FIG. 21 is a posterior view of the dynamic spine stabilization system ofFIG. 20A implanted and extending between a vertebra of the spine and twoadjacent vertebrae.

FIG. 22 is a posterior view of an alternative embodiment of a dynamicspine stabilization system in accordance with the present invention.

FIG. 23 is a lateral view (in partial cross-section) of an alternativeembodiment of a dynamic spine stabilization system in accordance withthe present invention.

FIG. 24A is a lateral view (in partial cross-section) of an alternativeembodiment of a dynamic spine stabilization system in accordance withthe present invention.

FIG. 24B is a lateral view of the dynamic spine stabilization system ofFIG. 24A.

FIG. 25 is a posterior view of the dynamic spine stabilization system ofFIG. 24A implanted and extending between a vertebra of the spine and twoadjacent vertebrae.

FIG. 26 is a lateral view of a further embodiment of a dynamic spinestabilization system in accordance with the present invention.

FIG. 27 is a lateral view of yet another embodiment of a dynamic spinestabilization system in accordance with the present invention.

FIG. 28 is a posterior view of an alternative embodiment of a dynamicspine stabilization system in accordance with the present invention.

FIG. 29 is a posterior view of an alternative embodiment of a dynamicspine stabilization system in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention include a system or implant andmethod that can dynamically stabilize the spine while providing for thepreservation of spinal motion. Alternative embodiments can be used forspine fusion.

Embodiments of the invention include a construct with an anchoringsystem, a deflection rod system and a vertical rod system.

An advantage and aspect of some embodiments of anchoring systems inaccordance with the present invention is that such embodiments include ahead or saddle that allows for appropriate, efficient and convenientplacement of the anchoring system relative to the spine in order toreduce the force that is placed on the anchoring system. Suchembodiments have enhanced degrees of freedom which contribute to theease of implantation of the anchor system and are designed to isolatethe head from the rest of the dynamic stabilization system and theforces that the rest of the dynamic stabilization system can place onthe anchor system and the anchor system/bone interface. Thus, the anchorsystem can provide a secure purchase in the spine.

An aspect and advantage of the invention is the ability to maximize therange of motion of the spine after embodiments of the dynamicstabilization, motion preservation implant of the invention areimplanted in a patient. While traditional solutions to back pain includefusion, discectomy, and artificial implants that replace spinestructure, embodiments of the present invention preserve the bone andligament structure of the spine and preserve a wide range of motion ofthe spine, while stabilizing spines that were heretofore unstable due todegenerative and other spinal diseases.

Still another aspect of the invention is the preservation of the naturalmotion of the spine and the maintenance of the quality of motion as wellas the wide range of motion so that the spine motion is as close to thatof the natural spine as possible. The present embodiments of theinvention allow for the selection of a less stiff, yet dynamicallystable implant for use in a non-fusion situation. A less stiff, yetdynamically stable implant relates directly to a positive patientoutcome, including patient comfort and the quality of motion of thespine.

In another aspect of the invention, load sharing is provided byembodiments, and, in particular, the deflection rod or loading rod ofthe embodiments. For embodiments of this invention, the terms“deflection rod” and “loading rod” can be used interchangeably.Accordingly this aspect of the invention is directed to restoring thenormal motion of the spine. The embodiment provides stiffness andsupport where needed to support the loads exerted on the spine duringnormal spine motion, which loads, the soft tissues of the spine are nolonger able to accommodate since these spine tissues are eitherdegenerated or damaged. Load sharing is enhanced by the ability toselect the appropriate stiffness of the deflection rod or loading rod inorder to match the load sharing characteristics desired. By selectingthe appropriate stiffness of the deflection rod or loading rod to matchthe physiology of the patient and the loads that the patient places onthe spine, a better outcome is realized for the patient. Prior toimplantation of the embodiment, the stiffness of the implant of thesystem can be selected among a number of loading rods. In other words,the stiffness is variable depending on the deflection rod or loading rodselected. In another aspect, the load sharing is between the spine andthe embodiment of the invention.

As the load is carried along the deflection rod or loading rod, theembodiments of the invention can be made smaller in order to fit in morespaces relative to the spine.

An aspect of the invention is to preserve and not restrict motionbetween the vertebra of the spine through the use of appropriatelyselected vertical rods (and optionally horizontal rods) of embodimentsof the invention.

Another aspect of the invention is the ability to control stiffness forextension, flexion, lateral bending and axial rotation, and to controlstiffness for each of these motions independently of the other motions.

An aspect of the invention is to use the stiffness and load bearingcharacteristics of super elastic materials.

Another aspect of the invention is to use super elastic materials tocustomize the implant to the motion preservation and the dynamicstabilization needs of a patient. An aspect of such embodiments of theinvention is to provide for a force plateau where motion of theimplantation system continues without placement of additional force ofthe bone anchor system, or, in other words, the bone/implantation systeminterface.

Accordingly, an aspect of the invention is to be able to selectivelyvary the stiffness and selectively vary the orientation and directionthat the stiffness is felt by varying the structure of the implantationsystem of the invention.

Another aspect of some embodiments of the invention is to prevent and/orprovide for any off-axis implantation by allowing the implantationsystem to have enhanced degrees of freedom of placement of the implant.

A further aspect of embodiments of the invention is to controlstabilized motion from micro-motion to broad extension, flexion, axialrotation, and lateral bending motions of the spine.

Yet another aspect of the embodiments of the invention is to be able torevise a dynamic stabilization implant should a fusion implant beindicated. This procedure can be accomplished by, for example, theremoval of the deflection rod system of the implantation system andreplacement with, for example, a stiffer deflection rod system.Accordingly, an aspect of the invention is to provide for a convenientpath for a revision of the original implantation system, if needed.

A further aspect of the invention, due to the ease of implanting theanchoring system, is the ability to accommodate the bone structure ofthe spine, even if adjacent vertebra are misaligned with respect to eachother.

A further aspect of the invention is that the implant is constructedaround features of the spine such as the spinous processes and, thus,such features do not need to be removed and the implant does not get inthe way of the normal motion of the spine features and the spinefeatures do not get in the way of the operation of the implant.

Another aspect of embodiments of the invention is the ability tostabilize two, three and/or more levels of the spine by the selection ofappropriate embodiments and components of embodiments of the inventionfor implantation in a patient. Further embodiments of the inventionallow for fused levels to be placed next to dynamically stabilizedlevels. Such embodiments of the invention enable vertebral levelsadjacent to fusion levels to be shielded by providing a more anatomicalchange from a rigid fusion level to a dynamically stable, motionpreserved, and more mobile level.

Accordingly, another aspect of the embodiments of the invention is toprovide a modular system that can be customized to the needs of thepatient. A Deflection rod system can be selectively chosen for theparticular patient as well the particular levels of the vertebrae of thespine that are treated. Further, the positioning of the embodiments ofthe invention can be selected to control stiffness and stability.

Another aspect of embodiments of the invention is that embodiments canbe constructed to provide for higher stiffness and fusion at one levelor to one portion of the spine while allowing for lower stiffness anddynamic stabilization at another adjacent level or to another portion ofthe spine.

Yet a further aspect of the invention is to provide for dynamicstabilization and motion preservation while preserving the bone andtissues of the spine in order to lessen trauma to the patient and to usethe existing functional bone and tissue of the patient as optimally aspossible in cooperation with embodiments of the invention.

Another object of the invention is to implant the embodiments of theinvention in order to unload force from the spinal facets and otherposterior spinal structures and also the intervertebral disc.

A further aspect of the invention is to implant the embodiment of theinvention with a procedure that does not remove or alter bone or tear orsever tissue. In an aspect of the invention the muscle and other tissuecan be urged out of the way during the inventive implantation procedure.

Accordingly, an aspect of the invention is to provide for a novelimplantation procedure that is minimally invasive.

Dynamic Stabilization, Motion Preservation System for the Spine:

Common reference numerals are used throughout the drawings and detaileddescription to indicate like elements; therefore, reference numeralsused in a drawing may or may not be referenced in the detaileddescription specific to such drawing if the associated element isdescribed elsewhere. Further, the terms “vertical” and “horizontal” areused throughout the detailed description to describe general orientationof structures relative to the spine of a human patient that is standing.

FIG. 1A is a posterior view (in partial cross-section) and FIG. 1B is alateral view of an embodiment of a deflection rod system implant 100 foruse with dynamic stabilization, motion preservation systems (alsoreferred to herein simply as “dynamic stabilization systems”) inaccordance with the present invention. The deflection rod system implant100 comprises a deflection rod system or deflection rod system engine110, an anchoring device 102 and a vertical rod 120. The deflection rodsystem 110 includes a deflection rod guide or shield 116 and adeflection rod 111 including an inner rod 112 within an outer shell 114.The deflection rod 111 can have a varying diameter along its length. Adecreasing diameter allows the deflection rods 111 to be more flexibleand bendable along the length deflection rod length to more evenlydistribute the load placed on the deflection rod system 100 by thespine. The outer shell 114 preferably is made of PEEK or othercomparable polymer and has a diameter that continuously decreases alongthe length of the deflection rod 111. The inner rod 112 can be comprisedof a super elastic material. Preferably, the super elastic material iscomprised of Nitinol (NiTi). In addition to Nitinol or nickel-titanium(NiTi), other super elastic materials include copper-zinc-aluminum andcopper-aluminum-nickel. However, for biocompatibility, nickel-titaniumis the preferred material. The inner rod 112, like the overalldeflection rod 111, can vary in diameter and shape, although in apreferred embodiment, the inner rod 112 is substantially cylindrical.

Alternatively, the diameter of the outer shell 114 can decrease indiscrete steps along the length of the distraction rod 111, with thediameter of one step not being continuous with the diameter of the nextadjacent step. Alternatively, for different force and load carryingcriteria the diameters of the deflection rod can continuously increasein diameter or can have discreet step increases in diameter along thelength of the deflection rod 111. Still further, the deflection rod 111can have at least one step of decreasing diameter and at least one stepof increasing diameter in any order along the length of the deflectionrod 111, as desired for the force and load carrying characteristics ofthe deflection rod 111.

The deflection rod 111 is arranged within the deflection rod guide orshield 116 which covers and, in this embodiment, substantially surroundsthe deflection rod 111. The deflection rod system 110 can be apreassembled unit provided to a surgeon for implantation by affixing thedeflection rod system 110 to a bone (e.g., the pedicle of a vertebra)using an anchoring device 102 such as a bone screw. The deflection rodsystem 110 is connected with the anchoring device 102 by an arm 130,which arm 130 can be integrally formed with the deflection rod system110, affixed to the deflection rod system 110 by one or more fastenersor fastening features (such as protruding structures that interlockinglyengage each other when coupled), press fit to the deflection rod system110, or otherwise fixedly secured to the deflection rod system 110. Inthe embodiment, the arm 130 includes an aperture 131 through which theanchoring device 102 is received and driven into the bone. The anchoringdevice 102 includes a head 104 that interferes with passage of theanchoring device 102 through the aperture 131. Threads 106 of theanchoring device 102 grip the bone to hold the arm 130 between the boneand the head 104, thereby affixing the arm 103 and by extension thedeflection rod system 110 to the bone. Preferably, the anchoring device102 is comprised of titanium; however, other biocompatible materialssuch as stainless steel and/or PEEK can be used. As will be appreciatedupon reflecting on the different embodiments, the structures describedherein can vary in size and shape based on factors such as material ofconstruction, anatomical structure of the implantation site,implantation technique and targeted system performance (e.g.,stiffness).

Referring to FIG. 2, the vertical rod 120 is connected to the deflectionrod 111 and can urge the deflection rod 111 in response to relativemovement of two vertebrae between which the vertical rod 120 extends. Inthe embodiment shown, a distal end of the deflection rod 111 can befixedly mated with a spherical (or semi-spherical) ball or joint 118that can pivot within a cradle at a proximal end of the vertical rod120. The vertical rod 120 can pivot in a posterior-to-anterior oranterior-to-posterior direction about the joint 118, and optionally canpivot slightly in a lateral direction. The pivoting motion can allowadjustment of the vertical rod 120 relative to the deflection rod system110 to ease manipulation of the dynamic stabilization system duringimplantation and optionally to reduce torque forces applied to thedeflection rod 111. A distal end of the vertical rod 120 can be fixedlyconnected with an upper (or lower) vertebra of the two vertebrae by anadditional anchoring device 152, such as a bone screw. The anchoringdevice 152 can include an arm 170 extending a clamp 162 that receivesand secures the vertical rod 120. The arm 170 extends laterally from theanchoring device 152 so that the anchoring device 152 can be positionedand secured to the upper pedicle 8 (a good source of bone for anchoring)while the clamp 162 can be aligned with the vertical rod 120 to receivethe vertical rod 120, which extends generally (though not necessarily)parallel to the spine. The dynamic stabilization system 100 comprisestwo substantially similar, mirrored structures connected at oppositepedicles 8,10 of the vertebrae 2,4. However, in alternative embodiments,the dynamic stabilization system can comprise dissimilar structures, forexample to accommodate anatomical asymmetry. FIG. 3A illustrates analternative embodiment wherein one or both of the deflection rod systemarms 330 and clamp arm 370 can include a secondary aperture forreceiving a locking screw 334,364 that can resist rotation of thecorresponding arm. FIG. 3B illustrates an alternative embodiment whereinthe deflection rod system arm 330 includes a secondary aperture forreceiving the locking screw 334, and wherein the clamp and clamp arm aresupplanted by an anchoring device 352 that receives the vertical rod 120over a bone screw thread. The anchoring device 352 can resemble theanchoring device 752 shown in FIGS. 7A, 7B, and described below in thedescription of FIGS. 7A, 7B. Such anchoring devices can resembleanchoring devices described in U.S. Provisional Application 61/031,598,entitled “A DEFLECTION ROD SYSTEM FOR A DYNAMIC STABILIZATION AND MOTIONPRESERVATION SPINAL IMPLANTATION SYSTEM AND METHOD” (SPART-01037US0),incorporated herein by reference. The alternative embodiment may reducetorque applied to the anchoring device 352 and simplify the anchoringdevice 352 to ease implantation of the anchoring device 352.

More lateral placement of the vertical rods provides for more stiffnessin lateral bending and an easier implant approach by, for example, aWiltse approach as described in “The Paraspinal Sacraspinalis-SplittingApproach to the Lumber Spine,” by Leon L. Wiltse et al., The Journal ofBone & Joint Surgery, Vol. 50-A, No. 5, July 1968, which is incorporatedherein by reference.

The stiffness of the deflection rod system 100 can preferably beadjusted by the selection of the materials and placement and diametersof the deflection rod system as well as the horizontal and verticalrods. Larger diameter rods would increase the resistance of thedeflection rod system 100 to flexion, extension rotation, and bending ofthe spine, while smaller diameter rods would decrease the resistance ofthe deflection rod system 100 to flexion, extension, rotation andbending of the spine. Further, continually or discretely changing thediameter of the deflection rods 111 along the length of the deflectionrods 111 changes the stiffness characteristics. Thus, with thedeflection rods 111 tapered toward the vertical rod 120, the deflectionrod system 100 can have more flexibility in flexion and extension of thespine. Further, using a super elastic material for the vertical rod 120in addition to the deflection rod 111 adds to the flexibility of thedeflection rod system 100. Further, the vertical rods 120, in additionto the deflection rods 111, can be made of titanium or stainless steelor PEEK should a stiffer deflection rod system 100 be required. Thus, itcan be appreciated that the deflection rod system 100 can selectivelyaccommodate the desired stiffness for the patient depending on thematerials uses, and the diameter of the materials, and the placement ofthe elements of the deflection rod system 100.

Should an implanted deflection rod system 100 need to be revised, thatcan be accomplished by removing and replacing the vertical rod 120and/or deflection rod system 110 to obtain the desired stiffness. By wayof example only, should a stiffer revised deflection rod system 100 bedesired, more akin to a fusion, or, in fact, a fusion, then thedeflection rod system 110 having the deflection rods 111 can be removedand replaced by a deflection rod system 110 having the deflection rods111 made of titanium, or stainless steel, or non-super elastic rods toincrease the stiffness of the system. This can be accomplished in someembodiments described herein by leaving the anchoring device 102 inplace and removing the existing deflection rod systems 110 and replacingthe deflection rod systems with deflection rod systems having stifferdistraction rods 111 and outer shells and associated vertical rods 120.

In alternative embodiments of methods of stabilizing vertebral motionsegments in accordance with the present invention, the dynamicstabilization system 100 can be implanted in an arrangement verticallyflipped from the arrangement of FIG. 2. As shown in FIG. 4, thedeflection rod system 110 is fixedly connected with the upper vertebraby the anchoring system 102. The vertical rod 120 is connected to thedeflection rod 111 and extends caudally to the lower vertebra. Thevertical rod 102 urges the deflection rod 111 in response to relativemovement of the two vertebrae between which the vertical rod 120extends. As with the previously described arrangement and as shown inFIG. 5, one or both of the deflection rod system arms 330 and clamp arms370 can include a secondary aperture for receiving a locking screw 334,364 that can resist rotation of the corresponding arm. Referring to FIG.6, in still further embodiments, one or both of the deflection rodsystem arms 630 and clamp arms 670 can be adapted to connect withhorizontal rods 680, 682 that extend between pedicles 8,10 of avertebra. The anchoring devices 602, 652 can include a U-shaped channelfor receiving the horizontal rod 680, 682, the horizontal rod being heldin the channel by a locking set screw 644, 654. The horizontal rods 680,682 are positioned between adjacent spinous processes 2, 4 associatedwith the vertebrae and can pierce or displace the interspinal ligamentwithout severing or removing tissue. The horizontal rods 680, 682 canresist rotation and can be used in place of locking screws. In apreferred embodiment, the horizontal rod 680,682 can be comprised oftitanium, stainless steel or PEEK or another biocompatible material, andthe first and second deflection rods or loading rods can be comprised ofa super elastic material. Preferably, the super elastic material iscomprised of Nitinol (NiTi). In addition to Nitinol or nickel-titanium(NiTi), other super elastic materials include copper-zinc-aluminum andcopper-aluminum-nickel. However, for biocompatibility, thenickel-titanium is the preferred material.

FIGS. 7A-9 illustrate a still further embodiment of a deflection rodsystem 700 in accordance with the present invention comprising andeflection rod system 710 connectable with an anchoring device 702 afterthe anchoring device 702 is secured to a pedicle. Such embodiments canreduce visual obstruction of the pedicle during seating of the anchoringdevice 702 by reducing the size of the structure seated. An anchoringblock 732 receives the anchoring device 702 through an aperture 731 andis secured to the pedicle as threads 106 of the anchoring device 702grip the bone and the head 704 is seated within the anchoring block 732.The anchoring block 732 includes an internal screw thread 734 through atleast a portion of the anchoring block 732 for receiving a screw 742 tosecure an deflection rod system arm 730 of the deflection rod system710. As in previous embodiments, the deflection rod system 710 comprisesa deflection rod shield or guide 716 and a deflection rod 711 includingan inner rod (not visible) within an outer shell 714. As shown, thedeflection rod system 710 is connected with an arm 730 having a curvedbase that meets a curved surface of the anchoring block 732 (FIG. 7C).The arm 730 can pivot slightly relative to the anchoring device 702,allowing the surgeon to adjust an angle of protrusion of the deflectionrod system 710 relative to the spine. The arm 730 is fastened to theanchoring block 732 by the screw 742 which is connected through a spacer744 having a surface in sliding contact with a curved surface of the arm730 to distribute force generally evenly along the arm 730 when arrangedat a desired orientation. In this arrangement, preferably, the joint 718is adjacent with and located over the anchor 702 in order to minimize oreliminate the transfer of torque forces from the rod 720 to the anchor702. Other complementary mating surfaces may be used to obtain thedesired relative motion.

A vertical rod 720 is connected to the deflection rod 711 and can urgethe deflection rod 711 in response to relative movement of two vertebraebetween which the vertical rod 720 extends. A distal end of thedeflection rod 711 can be fixedly mated with a spherical (orsemi-spherical) ball or joint 718 that can pivot within a cradle at aproximal end of the vertical rod 720. The vertical rod 720 can pivot ina posterior-to-anterior or anterior-to-posterior direction about thejoint 718, and optionally can pivot in a lateral direction. The pivotingmotion can allow adjustment of the vertical rod 720 relative to thedeflection rod system 710 to ease manipulation of the dynamicstabilization system during implantation and optionally to reduce torqueforces applied to the deflection rod 711. A distal end of the verticalrod 720 can be fixedly connected with an upper or lower vertebra of thetwo vertebrae by an additional anchoring device 752. The anchoringdevice can resemble anchoring devices as described in U.S. ProvisionalApplication No. 61/031,598. As shown, the anchoring device 752 includesa saddle 758 that can receive the vertical rod 720. A locking set screw754 can be urged along threads of the saddle 758 so that the locking setscrew 754 secures the vertical rod 758 against the U-shaped channel ofthe saddle 758. A bone screw thread 756 can optionally be mated with abody of the anchoring device 752 by a fastener 772 that permits at leastcranial-to-caudal pivoting. The saddle 758 can include a hex-shapedouter surface to assist in seating the bone screw 756 within the upperpedicle 8. As shown in FIGS. 8 and 9, the deflection rod system 700 canbe arranged with the deflection rod system 710 anchored to an upper oftwo vertebrae, or alternatively, the lower of two vertebrae.

FIG. 10 is a posterior view of a still further embodiment of adeflection rod system implant 1000 in accordance with the presentinvention comprising an deflection rod system 610 that is engaged duringspine extension, but not engaged during spine flexion. The deflectionrod system 610 and associated structures resemble the deflection rodsystem and associated structures of FIG. 6, and can be connected with ahorizontal rod 680 extending between pedicles of a vertebra. A verticalrod 1020 is connected at a proximal end to a deflection rod 111 of thedeflection rod system 610. The distal end of the vertical rod 1010 isunattached and slides within a boot 1090. The boot 1090 blocks movementof the vertical rod 1020 when the distal end of the vertical rod 1020abuts the base of the boot 1090, and further extension movement willcause the vertical rod 1020 to deflect the deflection rod 111. The boot1090 is preferably sized to accommodate movement of vertical rod 1020within the boot 1090 that spans a length of natural movement of thespine during extension, to avoid separation of the vertical rod 1020from the boot 1090. Alternatively, the distal end of the vertical rodcan include a ball or other slidable structure that is held within acavity of the boot, enabling the boot to resist both extension andflexion, and to permit a range of free motion determined by the surgeon.As shown, the boot 1090 is connected with an anchoring device 1052 by anarm 1070. A locking screw 1062 resists rotation of the boot 1090 aboutthe anchoring device 1052 in response to a force applied by the verticalrod 1020.

FIG. 11A is a posterior view (in partial cross-section) and FIG. 11B isa lateral view (in partial cross-section) of a still further embodimentof a deflection rod system implant 1100 for use with dynamicstabilization systems accordance with the present invention. Thedeflection rod system implant 1100 is adapted to support multiple motionsegments and comprises a first deflection rod system 1110 a connectedwith a vertical rod 1120 a extending cranially, a second deflection rodsystem 1110 b connected with a vertical rod 1120 b extending caudally,and an anchoring device 1102. The first and second deflection rodsystems 1110 a, 1110 b can have similar or different bending or loadcarrying or stiffness characteristics, as prescribed by the surgeon or aphysician. A common arm 1130 connects the first and second deflectionrod systems 1110 a, 1110 b with the anchoring device 1102. The arm 1130includes an aperture 1131 through which the anchoring device 1102 isreceived and driven into the bone. The anchoring device 1102 includes ahead 1104 that interferes with passage of the anchoring device 1102through the aperture 1131. Threads 1106 of the anchoring device 1102grip the bone to hold the arm 1130 between the bone and the head 1104,thereby affixing the arm 1103 and by extension the deflection rodsystems 1110 a, 1110 b. The arm 1130 can be adapted to connect with ahorizontal rod 1180 that extend between pedicles 10 of a vertebra. Thehorizontal rod 1180 can be received in U-shaped slots of the arm 1130and urged against the head 1104 of the anchoring device 1102 by alocking set screw 1144 having external threads that mate with internalthreads of the walls of the arm channel.

FIG. 12 is a lateral view of a deflection rod system implant 1200resembling the deflection rod system implant 1100 of FIG. 11B with acompressor element or cradle 1236 positioned within the channel andbetween the horizontal rod 1180 and anchoring device 1202. As shown, thehead 1204 of the anchoring device 1202 has a spherical or semi-sphericalshape, although alternatively the head can have some other shape thatcomplements the compressor element or cradle 1236 while permitted atleast limited movement between the two structures to allow flexibilityin relative arrangement during implantation. For example, the head canhave a rounded indention mateable with a spherical surface.

The compressor element or cradle 1236 has a generally cylindrical bodyso that the compressor element 1236 can fit within a bore of the arm1230. A posterior surface of the compressor element 1236 is concave andgenerally complementing the horizontal rod 1180 which rests thereon. Theanterior surface of the compressor 1236 is in sliding contact with thehead 1204 to allow the anchoring device 1202 to be positioned asappropriate. The locking set screw 1144 urges the horizontal rod 1180against the compressor element 1236, which in turn is urged against theanchoring device 1202. Alternatively, the compressor element 1236 andhead 1204 can have some other complementary shape that allows some or nosliding contact between the structures.

FIG. 13 is a posterior view of the deflection rod system implant 1200 ofFIG. 11 comprising the first deflection rod system 1110 a and seconddeflection rod system 1110 b secured to a vertebra common to twoadjacent motion segments targeted for stabilization by an anchoringdevice 1102. A first vertical rod 1120 a is connected to a deflectionrod 1111 a of the first deflection rod system 1110 a and extendscranially to the upper vertebra of the upper targeted motion segment,and is secured to the upper vertebra by a clamp 162. A second verticalrod 1120 b is connected to a deflection rod 1111 b of the seconddeflection rod system 1110 b and extends caudally to the lower vertebraof the lower targeted motion segment, and is secured to the lowervertebra by a clamp 162. The vertical rods 1120 a, 1120 b urgerespective deflection rods 1111 a,1111 b in response to relativemovement of the two vertebrae between which the vertical rods 1120a,1120 b extend. Preferably, vertical rod 1120 a is aligned withvertical rod 1120 b in order to reduce or eliminate torque forces. Anarm 1130 common to the deflection rod systems 1110 a,1110 b is connectedwith a horizontal rod 1180 that extends between pedicles of the commonvertebra to a complementary pair of deflection rod systems. Thehorizontal rod 1180 is positioned between adjacent spinous processes 2,4associated with the vertebrae and can pierce or displace the interspinalligament without severing or removing tissue. The horizontal rod 1180can resist rotation of the deflection rod systems 1110 a,1110 b and canbe used in place of locking screws.

FIGS. 14A and 14B illustrate yet another embodiment of a deflection rodsystem implant 1400 in accordance with the present invention comprisingan deflection rod system 1410 connectable with an anchoring device 1402,preferably after the anchoring device 1402 is secured to a pedicle. Anarm 1430 of the deflection rod system 1410 comprises a collar 1464 thatcan be received over a head 1404 of the anchoring device 1402 to capturea horizontal bar 1480. The arm 1430 can be secured to the head 1404 by acollar screw 1450. The horizontal bar 1480 can be held in place by oneor both of the arm 1430 which is urged against the horizontal bar 1480by the collar screw 1450, and a locking set screw 1458. Optionally, thehead 1404 of the anchoring device can be connected with a yoke 1407 by apin 1403 to allow the head 1404 to be pivoted during implantation. Suchan arrangement can allow a thread 106 of the anchoring device 1402 to beseated within the pedicle at an acute angle relative to a plane of thecollar.

Referring to FIG. 15, the deflection rod system implant 1400 of FIGS.14A and 14B is shown implanted between two vertebrae to stabilize themotion segment associated with the vertebrae. The deflection rod system1410 is anchored to the upper vertebra of the motion segment and avertical rod 120 is connected between a deflection rod 111 of thedeflection rod system 1410 and a clamp 162 connected with the lowervertebra by an anchoring device 152. FIG. 16 is a posterior view of astill further embodiment of a deflection rod system implant 1600 inaccordance with the present invention comprising an deflection rodsystem 1610 connected with an arm 1630 that resembles the arm 1430 ofFIG. 14A-15; however, the deflection rod system 1610 is connected withthe arm 1630 so that the deflection rod 111 extends toward the spinousprocess 2 rather than away from the spinous process (i.e., thedeflection rod system 1610 is “inboard). The clamp 162 is connected withthe anchoring device 152 by a clamp arm 1670 that likewise extendstoward a spinous process 4.

The embodiments described above comprise deflection rods extendinggenerally in a transverse direction to the orientation of the boneanchor screw. In still other embodiments, deflection rod systems can beoriented generally in a co-axial or collinear or parallel orientation toa bone anchor screw. Referring to FIGS. 17-22, the deflection rod systemcan extend substantially co-axial or parallel to the threaded shaft ofan anchoring device. As will be appreciated upon reflecting on theteaching provided herein, such embodiments can simplify implantation,reduce trauma to structures surrounding an implantation site, and reducesystem components.

FIG. 17 illustrates an embodiment of a deflection rod system implant1700 comprising an anchoring device 1702 with a cavity 1709 forreceiving a deflection rod system 1710. It has been observed thatacceptable anchoring can be achieved in a bone such as a pedicle using athread 1706 pattern that include deep threads 1706 x (i.e., having amaximum difference between inner diameter, D_(I1), and outer diameter,D_(O), of a shaft of the anchoring device) nearer the distal end of theshaft and comparatively shallow threads 1706 y nearer the shank 1705.The comparatively shallow threads 1706 y can enable a larger innerdiameter, D_(I2), of the anchoring device 1702 shaft which canaccommodate the deflection rod system 1710. In some embodiments, thecavity can have a size and shape that can accommodate deflection rodsystems having a range of different performance characteristics (e.g.,stiffness, range of motion). A physician or surgeon can implant ananchoring device 1702 selected independently from the deflection rodsystem 1710 and based on the anatomy into which it is implanted. Forexample, the anchoring device 1702 can be selected based on the locationof the vertebrae (e.g., L5-S1 vs. C7-T1) or the age and sex of thepatient. The deflection rod system 1710 can then be selected based onthe desired performance characteristics. The deflection rod system 1710can be seated within the cavity using myriad different techniques. Forexample, the distraction rod guide or shield 1716 can be press fit intothe walls of the cavity 1709, or the distraction rod guide 1716 can becemented or otherwise adhesively fixed to the walls of the cavity 1709.Alternatively, the distraction rod guide or shield 1716 can be capturedin the cavity 1709 by a locking set screw or ratchet feature. Further,the distraction rod guide 1716 (and deflection rod system 1710) can havea length longer than that of the cavity 1709 so that a portion of thedistraction rod guide 1716 extends outside of the cavity 1702 andposterior to the anchoring device 1702. One of ordinary skill in theart, upon reflecting on the teachings provided herein, will appreciatethe myriad ways in which the deflection rod system 1710 can be fixedlyassociated with an anchoring device 1702.

The distraction rod system 1700 of FIG. 17 generally includes less, orsimpler footprint than the previously described embodiments, potentiallyreducing the amount of displacement of tissue and/or bone, reducingtrauma to tissue and/or bone during surgery. Further, the smallerfootprint can reduce the amount of tissue that needs to be exposedduring implantation. Still further, arranging the deflection rod system1710 co-axial with a shaft of the anchoring device 1702 cansubstantially transfer a moment force applied by the deflection rodsystem 1710 from a moment force tending to pivot or rotate the anchoringdevice 1702 about the axis of the shaft, to a moment force tending toact perpendicular to the axis of the shaft. The distraction rod systemimplant 1700 can effectively resist repositioning of the deflection rodsystem 1710 and/or anchoring device 1702 without the use of lockingscrews or horizontal bars to resist rotation. Eliminating locking screwsand/or horizontal bars can reduce exposure of tissue and/or bone toforeign bodies.

FIG. 18 illustrates an alternative embodiment of a deflection rod systemimplant 1800 comprising an anchoring device 1802 with a cavity 1809 forreceiving a distraction rod 111. The embodiment resembles the deflectionrod system 1700 of FIG. 17; however, the distraction rod guide or shield1816 is integrally formed in a shank 1805 of the anchoring device 1802.The distraction rod guide or shield 1816 can be sized and shaped toprovide, in combination with the choice of inner rod 112 and outer shell114, a desired performance characteristic. Integrally forming thedistraction rod guide 1816 in a shank 1805 of the anchoring device 1802can potentially reduce a thickness otherwise required to accommodateseparate components. The distraction rod 111 can be mated with thedistraction rod guide 1816 applying similar techniques to matedistraction rods within previously described distraction rod guide orshield.

FIG. 19 illustrates a still further embodiment of a deflection rodsystem implant 1900 comprising an anchoring device 1902 with a cavity1909 including inner threads for receiving an deflection rod systemscrew 1913, with complementary external threads extending from andeflection rod system 1910. The deflection rod system screw 1913provides easy mating of the deflection rod system 1910 with theanchoring device 1902. The deflection rod system 1910 can furtherinclude a spherical (or semi-spherical) ball or joint 1918 that allowspivoting of a vertical rod 1920 connected with the deflection rod system1910 so that the vertical rod 1920 can be oriented in a needed directionas the deflection rod system 1910 is rotated and the deflection rodsystem screw 1913 is seated within the cavity 1909. The vertical rod1920 can then be pivoted into place extending between pedicles. Theembodiment of FIG. 19 can simplify and shorten surgery by providing aneasy technique for implanting the deflection rod system 1910.

FIGS. 20A and 20B illustrate yet another embodiment of a deflection rodsystem implant 2000 in accordance with the present invention comprisingan anchoring device 2002 with a housing 2009 for receiving a deflectionrod system 2010. The embodiment resembles the deflection rod systemimplant 1700 of FIG. 17; however, housing 2009 is connected with theanchoring device 2002 at the shank 2005, but is not formed in the shank2005. Depending on the outer diameter of the housing 2009 and the innerdiameter of the cavity that receives the deflection rod system 2010, thehousing 2009 permits use of one or both of (1) a threaded shaft 2006having a smaller diameter (for example for use in smaller bones, such asin the cervical region) and (2) a deflection rod system 2010 comprisinga deflection rod guide shield 2016 with a larger diameter (e.g., for usewith thicker (and stiffer) deflection rods). As shown, the housing 2009further comprises a threaded screw hole 2057 extending along an axis atan acute angle to the axis of the threaded shaft. The threaded screwhole 2057 receives a locking set screw 2058 that when seated (FIG. 20B)protrudes into the housing 2009 or against the deflection rod system2010, where the deflection rod system 2010 is seated within the housing2009. The locking set screw 2058 holds the deflection rod system 2018 inplace within the housing 2009. In this embodiment, a deflection rodsystem 2010 can be selected to have an appropriate stiffness for thepatient. Further, if several deflection rod system implants 2000 areused in a patient, each deflection rod system 2010, if desired, can havea different stiffness.

FIG. 21 is a posterior view of the deflection rod system implant 2000 ofFIGS. 20A and 20B implanted between pedicles 8,10 of adjacent vertebraeof a targeted motion segment. As shown, both ends of a vertical rod 2020connected with the deflection rod system implant 2000 is connected withan deflection rod system 2010, in contrast to previous figures.Alternatively, one end of the vertical rod 2020 can be connected with ananchoring device such as described above, for example in FIG. 9. As willbe appreciated, the deflection rod system implant 2000 has a smallfootprint from a posterior perspective.

FIG. 22 is a posterior view of still another embodiment of a deflectionrod system implant 2200 in accordance with the present invention adaptedto support multiple motion segments. An anchoring device 2202 resemblesthe anchoring devices of FIGS. 17-20B and includes an outer wall 2203having a hex portion for gripping using a torque wrench or other toolduring implantation of the anchoring device 2202 in a bone. An anchoringdevice 2202 is secured to the two pedicles 10 of a vertebra common tothe two motion segments to be supported. A vertical rod 2220 connectedwith an deflection rod system 2210 mated with the anchoring device 2202,extends between the vertebra and an upper vertebra of the upper motionsegment, and is connected to a pedicle 8 of the segment by an upperanchoring device 752. As above, the vertical rod 2220 is connected tothe deflection rod and can deflect the deflection rod in response torelative movement of two vertebrae between which the vertical rod 2220extends. Another vertical rod 2222 includes a yolk 2223 resembling abox-end wrench with a shape generally complementing the hex pattern ofthe outer wall of the bone anchor. The yolk 2223 is received over theouter wall 2203 of the anchoring device 2202, and can resist rotationthe vertical rod 2222 relative to the anchoring device 2202. Thevertical rod 2222 extends to the lower vertebra of the lower motionsegment, and is connected to a pedicle 12 of the motion segment by alower anchoring device 752. The vertical rod 2222 can resist movementbetween vertebrae 4 and 6, and thus supplement or substitute for otherfusion devices, for example.

FIG. 23 is a lateral view (in partial cross-section) of an alternativeembodiment of a deflection rod system implant 2300 for use with dynamicstabilization systems in accordance with the present invention andadapted to dynamically support multiple motion segments of the spine.The deflection rod system implant 2300 resembles the deflection rodsystem implant 1100 of FIG. 11A, but includes deflection rod systemsgenerally oriented in an anterior-to-posterior direction. The deflectionrod system implant 2300 is adapted to support multiple motion segmentsand comprises a first deflection rod system 2310 a connected with avertical rod 120 a extending cranially, a second deflection rod system2310 b connected with a vertical rod 120 b extending caudally, and ananchoring device 2302. The first and second deflection rod systems 2310a, 2310 b can have similar or different bending characteristics, asprescribed by the surgeon or a physician. A common arm 2330 connects thefirst and second deflection rod systems 2310 a, 2310 b with theanchoring device 2302. The orientation of the deflection rod systems2310 a, 2310 b can reduce the moment force that tends to cause rotationof the arm 2330; however, in other embodiments it may be desirable toinclude a head capable of receiving a horizontal rod to further resistmoment force. In this embodiment, the deflection rod systems 2310 a,2310 b are substantially parallel.

FIG. 24A is a lateral view (in partial cross-section) and FIG. 24B is acranial view (in partial cross-section) of still another embodiment of adeflection rod system implant 2400 for use with dynamic stabilizationsystems accordance with the present invention and adapted to dynamicallysupport multiple motion segments is shown. The deflection rod systemimplant 2400 resembles the deflection rod system implant 2300 of FIG.23. An arm 2430 that is mated with the anchoring device 2402 after theanchoring device 2402 has been implanted within a bone. The arm 2430receives a locking screw 2440 having threads that complement threads ofa screw hole within the head 2404 of the anchoring device 2402. Thelocking screw 2440 fixedly connects the arm 2430 to the anchoring device2402 when the locking screw 2440 is seated within the head 2404. Theembodiment also includes a distraction rod guide or shield 2416integrally formed with the arm 2430. In this embodiment, the deflectionrod systems 2410 are substantially parallel. As seen in FIGS. 24A, 24Bthe arm 2430 can connect to the head 2404 in a number of orientations.This can be accomplished with an arm 2430 with a convex surface thatmates with a concave surface of the head 2404 as shown, by way ofexample only, as depicted in FIG. 7C.

FIG. 25 is a posterior view of the deflection rod system implant 2300 ofFIG. 23 comprising the first deflection rod system 2310 a and seconddeflection rod system 2310 b secured to a vertebra common to twoadjacent motion segments or vertebrae targeted for stabilization by ananchoring device. A first vertical rod 2320 a is connected to adeflection rod 2311 a of the first deflection rod system 2310 a andextends cranially to the upper vertebra of the upper targeted motionsegment, and is secured to the upper vertebra by an upper anchoringdevice 752. A second vertical rod 2320 b is connected to a deflectionrod 2311 b of the second deflection rod system 2310 b and extendscaudally to the lower vertebra of the lower targeted motion segment, andis secured to the lower vertebra by a lower anchoring device 752. Thevertical rods 2320 a, 2310 b deflect respective deflection rods 2311 a,2311 b in response to relative movement of the two vertebrae betweenwhich the vertical rods 2320 a, 2320 b extend.

FIG. 26 illustrates an embodiment of a deflection rod system implant2600 comprising an anchoring device 2602 with a cavity 2609 forreceiving a deflection rod system 2610. As mentioned above, it has beenobserved that acceptable anchoring can be achieved in a bone such as apedicle using a thread 2606 pattern that include deep threads 2606 x andshallow threads 2606 y. The anchoring device 2602 can have a length suchthat when implanted a portion of the anchoring device 2602 further fromthe deflection rod system 2610 is seated within cancellous bone while aportion of the anchoring device 2602 nearer the deflection rod system2610 is seated within cortical bone. Screw threads 2606 y having a highpitch (i.e., having a comparatively large gap between threads) and deepthreads are usable with satisfactory results in cancellous bone, whichbone is an osseous tissue with a low density strength but high surfacearea. Screw threads 2606 x having a low pitch and shallow threads areusable with satisfactory results in cortical bone, which bone is anosseous tissue with a high density strength. The diameter, D_(I2), ofthe anchoring device shaft can be expanded along a portion of the shaftthat is seated within the cortical bone and/or a portion of the shaftthat accommodates the deflection rod system 2610. Expanding the diameterof the shaft can allow the threads 2606 yx to cut new thread patternswithin the cortical bone, and can accommodate a deflection rod system2610 (or range of deflection rod systems) having a larger diameter.Further, the diameter of the shaft can be larger when the corticalthreads 20606 y are, as the vertebral bone is thicker in this area. Forthe same reason, the corresponding diameter of the bone as shown in FIG.27 can be larger.

FIG. 27 illustrates a still further embodiment of a deflection rodsystem implant 2700 comprising an anchoring device 2702 including anexternal thread pattern resembling the external thread pattern of FIG.26, and further including a cavity 2709 with inner threads for receivingan deflection rod system screw 1913, with complementary external threadsextending from an deflection rod system 1910. The deflection rod systemscrew 1913 provides easy mating of the deflection rod system 1910 withthe anchoring device 1902. The deflection rod system 1910 can furtherinclude a spherical (or semi-spherical) ball or joint 1918 that allowspivoting of a vertical rod 1920 connected with the deflection rod system1910 so that the vertical rod 1920 can be oriented in a needed directionas the deflection rod system 1910 is rotated and the deflection rodsystem screw 1913 is seated within the cavity 1909. The vertical rod1920 can then be pivoted into place extending between pedicles.

Referring again to FIG. 22, multiple motion segments can be stabilizedby stringing together vertical rods and deflection rod systemsindividually selected for the corresponding motion segment. As shown inFIG. 22, the yoke 2223 of a vertical rod 2222 is fitted over the outerwall 2203 of a deflection rod system 2210. An opposite end of thevertical rod 2222 is connected to an anchoring device 2202. However, instill other embodiment (as shown in FIG. 28), the vertical rod 2822 canbe connected with a second deflection rod system 2810 b anchored by ananchoring device 2802 b to a pedicle 12 of a lower vertebra of themotion segment. The deflection rod system 2810 b allows controlledrelative movement of the two vertebrae. Systems and methods inaccordance with the present invention can comprise a series of implantsconnected with, and selected for the corresponding motion segment. Theimplants can comprise vertical rods rigidly connected between vertebraeas shown in FIG. 22 (for example to support fusion), or alternativelythe vertical rods can be dynamically connected between vertebrae by adeflection rod system as shown in FIG. 28. Any combination of implantscan be used having a stiffness selected for the respective motionsegment. For example, FIG. 29 illustrates dynamic stabilization of threemotion segments with two yoked vertical rods 2922 a, 2922 b fitted overdynamic stabilization systems 2810 a, 2810 b anchored at an uppervertebra of the targeted segment.

While the vertical rods 2822, 2922 of FIGS. 28 and 29 are shown to beconnected with dynamic stabilization systems implanted in respectivepedicles, embodiments of systems and methods can comprise vertical rodsthat are connected with dynamic stabilization systems after implantationof dynamic stabilization systems. The vertical rods 2822, 2922 can beattachable with a dynamic stabilization system at or near the connectionwith the spherical ball joint. Such an arrangement can allow a yoke of avertical rod to be placed over and around the outer wall of a dynamicstabilization system (or simply past the spherical ball joint in astaging position for further adjustment) without interference from thevertical rod of that dynamic stabilization system.

It is proposed that a preferred embodiment may have the followingpreferred dimensions, although dimension can vary substantially based ona number of performance factors.

-   -   Inner rod having a diameter of about 0.080 inches.    -   Outer shell having a major diameter of about 165 inches and the        tapered portion tapers at about 2.5 degrees per side.    -   Shield and deflection guide having a housing diameter of about        0.265 inches.    -   The deflection rod is secured to the deflection guide along a        length of about 0.200 inches from the end of the deflection rod        system.    -   The deflection rod system has a working length from the end of        the system to the center of the ball joint of about 1.040 less        the press fit length of about 0.200 which is length of about        0.840.    -   The overall length of the deflection rod system is about 1.100        inches.    -   The spherical ball in the ball and socket joint that secures the        vertical rod to the deflection rod system has a diameter of        about 188 inches.    -   The vertical rod has a diameter of about 0.150 inches.

Materials of Embodiments of the Invention:

In addition to Nitinol or nickel-titanium (NiTi) other super elasticmaterials include copper-zinc-aluminum and copper-aluminum-nickel.However for biocompatibility the nickel-titanium is the preferredmaterial.

As desired, the implant can, in part, be made of titanium or stainlesssteel. Other suitable material includes by way of example onlypolyetheretherketone (PEEK), polyetherketoneketone (PEKK),polyetherketone (PEK), polyetherketoneetherketoneketone (PEKEKK), andpolyetheretherketoneketone (PEEKK). Still, more specifically, thematerial can be PEEK 450G, which is an unfilled PEEK approved formedical implantation available from Victrex of Lancashire, GreatBritain. (Victrex is located at www.matweb.com or see Boedekerwww.boedeker.com). Other sources of this material include Gharda locatedin Panoli, India (www.ghardapolymers.com).

As will be appreciated by those of skill in the art, other suitablesimilarly biocompatible thermoplastic or thermoplastic polycondensatematerials that resist fatigue, have good memory, are flexible, and/ordeflectable have very low moisture absorption, and good wear and/orabrasion resistance, can be used without departing from the scope of theinvention.

Reference to appropriate polymers that can be used in the spacer can bemade to the following documents. These documents include: PCTPublication WO 02/02158 A1, dated Jan. 10, 2002, entitled“Bio-Compatible Polymeric Materials;” PCT Publication WO 02/00275 A1,dated Jan. 3, 2002, entitled “Bio-Compatible Polymeric Materials;” andPCT Publication WO 02/00270 A1, dated Jan. 3, 2002, entitled“Bio-Compatible Polymeric Materials.”

The foregoing description of preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many embodiments were chosenand described in order to best explain the principles of the inventionand its practical application, thereby enabling others skilled in theart to understand the invention for various embodiments and with variousmodifications that are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the claims andtheir equivalents.

1. An implant adapted to be implanted in a spine comprising: a firstdeflection rod system including a first rod that is deflectable; asecond deflection rod system including a second rod that is deflectable;a mount that is connected with said first deflection rod system and thatis connected with said second deflection rod system; wherein said firstdeflection rod system and said second deflection rod system are aboutparallel; a bone anchor; and said bone anchor being adapted to securesaid mount to the bone of a patient.
 2. The implant of claim 1 whereinsaid bone anchor is about parallel to said first deflection rod systemand said second deflection rod system.
 3. The implant of claim 1 with afirst connector rod movably connected to said first rod, and a secondconnector rod movably connected to said second rod.
 4. The implant ofclaim 1 wherein said first deflection rod system includes a first outershell located about said first rod and a first deflection limitingshield located about said first outer shell which limits the deflectionof said first rod and said first outer shell; and said second deflectionrod system includes a second outer shell located about said second rodand a second deflection limiting shield located about said second outershell which limits the deflection of said second rod and said secondouter shell.
 5. The implant of claim 1 wherein said mount ispositionable relative to said bone anchor.
 6. The implant of claim 1wherein said first deflection rod system has different spinestabilization characteristics from said second deflection rod system 7.The implant of claim 1 wherein said first deflection rod is comprised ofa super elastic material and said second deflection rod is comprised ofa super elastic material.
 8. The implant of claim 1 wherein said firstdeflection rod system is connected to a first distal end of said mountand said second deflection rod system is connected to a second distalend of said mount with said bone anchor located between said firstdistal end and said second distal end.
 9. The implant of claim 1 whereinsaid first and second deflection rod systems and said bone anchor areall aligned.
 10. The implant of claim 1 wherein said first deflectionrod system includes a first outer shell located about said first rod andsaid mount includes a first deflection limiting shield located aboutsaid first outer shell which limits the deflection of said first rod andsaid first outer shell; and said second deflection rod system includes asecond outer shell located about said second rod and said mount includesa second deflection limiting shield located about said second outershell which limits the deflection of said second rod and said secondouter shell.
 11. The implant of claim 4 wherein said first and secondrods are comprised of a super elastic material and said first and secondouter shells are comprised of a bio-compatible polymer.
 12. The implantof claim 10 wherein said first and second rods are comprised of a superelastic material and said first and second outer shells are comprised ofa bio-compatible polymer.
 13. An implant adapted to be implanted in aspine comprising: a first deflection rod system including a first rodthat is deflectable and a first outer shell and a first shield thatlimits the deflection of said first rod and said first outer shell; asecond deflection rod system including a second rod that is deflectableand a second outer shell and a second shield that limits the deflectionof said second rod and said second outer shell; a mount that isconnected with said first deflection rod system and that is connectedwith said second deflection rod system; wherein said first deflectionrod system and said second deflection rod system are about parallel; afirst connector rod movably connected to said first rod, and a secondconnector rod movably connected to said second rod; and a bone anchor;wherein said mount is positionable relative to said bone anchor; andsaid bone anchor being adapted to secure said mount to the bone of apatient.
 14. The implant of claim 13 wherein said bone anchor is aboutparallel to said first deflection rod system and said second deflectionrod system.
 15. The implant of claim 13 wherein said first deflectionrod system has different spine stabilization characteristics from saidsecond deflection rod system
 16. The implant of claim 13 wherein saidfirst deflection rod is comprised of a super elastic material and saidsecond deflection rod is comprised of a super elastic material.
 17. Theimplant of claim 13 wherein said first deflection rod system isconnected to a first distal end of said mount and said second deflectionrod system is connected to a second distal end of said mount with saidbone anchor located between said first distal end and said second distalend.
 18. The implant of claim 13 wherein said first and seconddeflection rod systems and said bone anchor are all aligned.
 19. Theimplant of claim 13 wherein said first and second rods are comprised ofa super elastic material and said first and second outer shells arecomprised of a bio-compatible polymer.
 20. The implant of claim 13wherein said first and second rods are comprised of Nitinol and saidfirst and second outer shells are comprised of PEEK.